Dokument
UMA0132
Rev
3
Sid
13 (16)
Test gas verification
If the measurement of a sensor is to be verified, a test gas with carefully determined
concentration of CO and CO
2
must be used. For zero calibration pure nitrogen or air
that has passed through a chemical absorber should be used. In fresh air the carbon
monoxide concentration is nearly zero. The Zero calibration kit can be used to
produce carbon dioxide free air. Check the CO and CO
2
values of the display or the
voltage of the output 1 for CO and the voltage of the output 2 for CO
2
with a
multimeter when the values have stabilized.
When a zero calibration shall be executed a plastic tube with 2.2 mm outer diameter
and 0,8 mm inner diameter shall be inserted in marked holes of the sensor. Plastic
tubing is connected to the tube. The gas flow should be between 0.3 and 1.0 l/min.
The yellow LED flashes when a calibration is executed .A calibration will only be
executed if the gas concentration is stable. If the yellow LED does not flash after 8
seconds no calibration has been executed. Then try to do another calibration.
Marking
Function
CALb CO2
Background calibration = CO
2
sensor calibration with fresh air
. An easy way to
correct the zero point error. The sensor needs fresh air (380-420 ppm CO
2
). The CO
2
sensor is calibrated to 400 ppm CO
2
.
CAL CO
Zero point calibration
of the CO sensor
with fresh air. The CO sensor is calibrated to
0 ppm CO
Figure 11 The PCB with the calibration jumper in default position. An enlarged part of the PCB with
marked gas inlets and jumper positions for calibration is shown at right.
ESC
MENU
ESC
MENU
Gas inlet CO2
Gas inlet CO2
